Ultra high frequency ignition device



N. l. KORMAN ULTRA-HIGH FREQUENCY GNLTIoN DEVICE June 10, 1947,

Filed Aug. 19, 1945 nventor Gttomeg Patented June 10, 1947 ULTRA HIGHFREQUENCY IGNITION DEVICE Nathaniel I. Korman, Camden, N. J., assignorto Radio Corporation of America, a corporation of Delaware ApplicationAugust 19, 1943, Serial No. 499,294

'I'his invention relates generally to ignition systems for internalcombustion engines and particularly to ignition plugs forsystemsemploying ultra-high frequency energy suitably applied to said plugs forestablishing ignition temperatures.

Present ignition systems for aircraft use have the distinct disadvantagethat considerable radio interference is generated by the highpotentials, bythe wave form thereof, and by comparatively lowfrequencies involved. Numerous ignition shielding devices are known fordecreasing the inherent radio interference set up by said systems, butsuch devices have limited utility due to Wide variations in moisture,pressure and temperature gradients encountered in radio aircraftoperation. For example, When an airplane flies through a cloud,considerable condensation may occur within the shielding surrounding thehigh tension spark plug leads, resulting in reduced eiiiciency of theignition system and objectionable radio interference. Moreover, at loWpressures experienced at extremely high altitudes, sparkover may occurin the ignition distribution system thereby causing engine failure.Various methods, including the use of air pumps, have been devised forexhausting the moisture or increasing the air pressure Within the hightension electrostatic ignition shielding, but the additional apparatusrequired adds Weight and has other serious disadvantages.

The instant invention is an improvement upon the system described in thecopending U. S. application of Francis X. Rettenmeyer Ser. No. 445,046led May 29, 1942, entitled Ultra high frequency ignition system. Thatcopending application discloses and claims an ultra-high frequencyignition system which utilizes the advantages of low inherent radiationfrom low impedance high frequency transmission lines or from Waveguides. The Wave guides couple an ultra-high frequency pulse generatorto tuned sparking devices which comprise quarter wave sections ofconcentric transmission line. The system thus described, by utilizingignition voltages of ultra-high frequency considerably above the normalfrequencies used for radio transmission, and by employing low impedanceignition energy transmission lines, greatly reduces radio interferenceand provides efficient ignition under normally adverse conditions.

The instant invention comprises several embodiments and modificationsthereof of ignition plugs adapted for use with wave-guide ultrahighfrequency ignition distribution systems. Briefly, the variousembodiments of the inven- 7 Claims. (Cl. 315-39) tion each comprise acylindrical conductive member'formed to receive a waveguide distributionelement, and threaded to engage a threaded spark plug port in aninternal combustion engine. An insulating member is disposed Within aconstricted portion of the cylindrical conductive member which extendsinto the spark plug port to provide an effective gas seal. A conductiveelement which is resonant at the operating ultra-high frequency israised in temperature, or forms a spark discharge, in response to theultrahigh frequency energy of the field impressed thereon.

One embodiment of the invention includes a conductive disc including aresonant aperture of predetermined shape and dimensions to provide aspark discharge at a restricted portion of said aperture in response toimpressed ultra-high frequency energy. A second modification of theinvention includes a section of wave guide having a length equivalent toone half wavelength at the operating frequency and having conductiveportions at each end to provide spark gaps for the ultra-high frequencyenergy impressed thereon. A third embodiment of the invention comprisesa resonant conductive ring supported by a suitable insulating spidertransversely of the constricted Wave guide portion which extends intothe cylinder spark plug port. Ultra-high frequency energy generatescirculating currents on the surface of the resonant conductive ringwhich heat the surface of the ring to ignition temperatures. When theultra-high frequency energy is not impressed upon the ring the massthereof provides suiiicient cooling by conduction from the surfaceportions to the interior portions thereof.

Among the objects of the invention are to provide an improved method ofand means for providing ultra-high frequency ignition in an internalcombustion engine. Another object of the invention is to provide animproved ultra-high frequency ignition plug for use with a wave guidetype ignition distribution system. An additional object of the inventionis to provide an improved ultra-high frequency ignition plug for usewith a wave guide distribution system wherein a spark discharge isprovided across a restricted portion of a resonant conductive elementforming a portion of said plug. An additional object of the invention isto provide an improved ultrafurther object of the invention is toprovide an ultra-high frequency ignition plug for use with a wave guidetype ignition distribution system wherein the surface of a resonantconductive element is heated to ignition temperatures by circulatingcurrents induced therein, and wherein cooling of the heated conductiveelement is provided by conduction from the surface portions to theinterior portions thereof.

rIhe invention will be further described by reference to theaccompanying drawing of which Figure l is an elevational cross-sectionalview of one embodiment thereof, Figures 2 and 3 are cross-sectionalviews of different modifications of Figure l taken along the sectionline II-II; Figure 4 is a cross-sectional elevational view of a secondembodiment of the invention; Figure 5 is a sectional view of theembodiment illustrated in Figure 4 taken along the section line V-V;Figure 6 is a cross-sectional elevational view of a third embodiment ofthe invention and Figure 7 isV a sectional View of Figure 6 taken alongthe section line VII- VIL Similar reference characters are applied tosimilar elements throughout the drawing.

Referring to Figure l, a cylindrical conductive ignition plug I includesan enlarged portion 2 having slots 3' adapted to provide spring contactsurfaces for receiving an ultra-high frequency ignition distributionwave guide d. A constricted portion 5 of the ignition plug I includes athreaded sleeve 6 adapted to engage the threads of a conventional sparkplug port of an internal combustion engine. A portion 1 of the threadedsleeve 6 may be flattened to receive a Wrench for tightening the pluginto the spark plug port. An

insulating plug 8 is sealed within the constricted portion 5 of theignition plug I to provide an effective gas seal for the internalcombustion engine cylinder.

Adjacent the end of the constricted plug portion 5, remote from theenlarged plug portion 2, a conductive ignition element 9 is disposedtransversely of the constricted portion 5 of the wave guide plug. Aspark discharge is caused to occur across a gap Iii when the conductiveelement S is subjected to ultra-high frequency energy through the Waveguide system. The ultra-high frequency energy may be pulsed andcommutated to provide suitably timed pulses of ignition en- A ergy inthe manner described in the aforementioned copending application.

Figure 2 illustrates the details of a typical conductive sparkingelement 9 as employed in the device described in Figure 1. Theconductive disc 9 disposed transversely of the constricted ignition plugportion 5 includes a "resonant aperture formed by two circular holes II,II connected by a narrow slot Iii. Ultra-high frequency energy in theform of an electric field in the wave guide induces circulating currentsin the conductive disc 9 which provides suiiicient voltage between theadjacent sides of the narrow slot ID to provide a spark discharge acrosssaid slot in response to the pulsed and commutated ultrahigh lfrequencyenergy.

Figure 3 is similar to Figure 2 with the exception that the conductivedisc 9 includes two parallel disposed slots I2, I2' interconnected by anarrow slot Ii). The spark discharge occurs between the closely spacedsides of the narrow slot or aperture Il) in response to voltages inducedtherein by circulating currents caused by ultra-high frequency energyapplied thereto.

Figure 4 is similar in all respects to Figure 1 with the exception thatthe constricted portion of the ignition plug has a length of the orderof 1/2 wavelength at the operating frequency. Conductive elements I3,I3', forming spark gaps I4, I4', are disposed adjacent the ends of theconstricted plug portion 5. Ultra-high frequency energy applied to theconstricted plug portion induces voltages between the spaced conductiveelements forming the gaps I4, I4 to provide a spark discharge across thegaps which may loe employed for internal combustion ignition.Preferably, the gap I4 is shorter than .fthe gap III in order to insurethat sparking always will occur at the gap I4 which is disposed Withinthe engine cylinder.

Figure 5 is a section of the device described in Figure 4 taken alongthe section line V-V to illustrate the conformation of the spark gapemployed.

Referring to Figures 6 and '7, the device described is similar toFigures 1 andl 4 with the eX- ception that a relatively short insulatingplug 8r is employed, and ignition is accomplished byheating a metallicelement instead of by a sparkdischarge. An insulating spider I5 disposedtransversely of the constricted portion 5V of the ignition plug Iadjacent the end thereof remote from the enlarged portion 2, supports aconductive ring I6. The conductive ring I6 is resonant at the operatingignition frequency, and the surface portions thereof are heated toignition temperatures by circulating currents induced therein by theignition energy field within the constricted portion of the ignitionplug.

At operating frequencies of the order o-f 10,000 megacycles, thecirculating currents penetrate the metallic ring only a few microns,thereby providing extremely high-surface temperatureswith relatively lowpower. Also, as soon as the ignition energy is interrupted by thedistributing device in the ignition pulse generator, the surfaceV be inany convenient form and of any material V providing suitable resistanceto corrosion and carbon accumulation. Likewise, the conductivel discsproviding sparking electrodes in the devices described in Figures 1 to 5inclusivemay be varied in size and shape and constructed of suitablematerials to minimize wear and carbon accumulation. It should further beunderstood that the enlarged portion of the ignition plug may becircular, square or rectangular in cross-section, or of any other shapeadapted to receive the particular type of wave guide employed forignition distribution from the ignition pulse generator.

I claim as my invention:

1. A tuned gas ignition device for ultra-high frequency ignition energyderived from a Wave guide energy distribution system comprising a hollowconductive dielectric guide element having a first portion formed toengage said wave guide and having a second portion formed to engage acomplementarily shaped utilization device, and conductive ignition meanstuned to said frequency and disposed transversely ofV said device at theend thereof remote from` and in op'- erative relation with respect tosaid' hollow, conduct-ive element whereby ignition currents are inducedin said means in response to ultra-high frequency energy derived fromsaid wave guide.

2. A tuned gas ignition device for ultra-high frequency ignition energyderived from a wave guide energy distribution system comprising a hollowconductive dielectric guide element having a iirst portion formed toengage said wave guide and having a second portion formed to engage acomplementarily shaped utilization device, and conductive ignition meansdefining a resonant aperture tuned to said frequency and disposedtransversely of said device at the end thereof remote from said hollowconductive element to induce in said means an ignition current inresponse to ultra-high frequency energy derived from said wave guide.

3. A tuned gas ignition device for ultra-high v frequency ignitionenergy derived from a wave guide energy distribution system comprising ahollow conductive dielectric guide element having a iirst portion formedto engage said wave guide and having a second portion formed to engage acomplementarily shaped utilization device, and conductive ignition meanstuned to said frequency and disposed transversely of said device at theend thereof remote from said hollow conduc tive element whereby ignitioncurrents are induced in said means in response to ultra-high frequencyenergy derived from said wave guide.

4. Apparatus of the type described in claim 1 comprising an ignitionplug for an internal combustion device, and including a dielectricelement providing a gas seal between said portions of said conductiveelement to prevent gas leakage from said combustion device through saidignition plug.

5. A tuned gas ignition device for ultra-high frequency ignition energyderived from a Wave guide energy distribution system comprising a hollowconductive dielectric guide element having a first portion formed toengage said wave guide and having a second portion formed to engage acomplementarily shaped utilization device, and a pair of conductivemeans spaced an even multiple of one-quarter wavelength and tuned tosaid frequency andV disposed transversely of said device at the endthereof remote from said hollow conductive element to induce in saidmeans an ignition current in response to ultrahigh frequency energyderived from said wave guide.

6. Apparatus of the type described in claim 5 comprising an ignitionplug for an internal combustion device, and including dielectric meansinterposed between said conductive means and providing a gas sealbetween said portions of said conductive element to prevent gas leakagefrom said combustion device through said ignition plug.

7. A tuned gas ignition device for ultra-high frequency ignition energyderived from a Wave guide energy distribution system comprising a hollowconductive dielectric guide element having a first portion formed toengage said Wave guide and having a second portion formed to engage acomplementarily shaped utilization device, and conductive ignition meansdening a current discharge path tuned to said frequency and disposedtransversely of said device at the end thereof remote from said hollowconductive element to induce in said means an ignition current inresponse to ultra-high frequency energy derived from said wave guide.

NATHANIEL I. KORMAN.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,106,771 Southworth Feb. 1, 19382,129,711 Southworth Sept. 13, 1938 2,129,713 Southworth Sept. 13, 19382,190,668 Llewellyn Feb. 20, 1940 2,372,429 Jones Mar. 27, 1945

